The present invention relates to an implant fixture that functions as a combined retainer and stabilizer for a prosthesis filled and fixed in a cavity formed in the bone of toothless gums, and an implant fixture forceps which enables the implant fixture to be easily fitted in the cavity formed in the bone.
Generally, prosthetic dentistry has so far been carried out with bridges and dentures.
However, a problem with the bridge prosthetic dentistry is that sound natural teeth on both sides of a toothless gum site are cut to form a pier and a prosthesis is fixed on a metal member to engage the pier at a position corresponding to the toothless gum site; it is not only required to cut sound teeth, but deossification is also induced at the position corresponding to the toothless gum site, since no direct occlusal pressure is applied on the prosthesis at that position.
In denture prosthetic dentistry, a denture made of synthetic resin and the like is used as a prosthesis, and occlusal force acting on the prosthesis is born by remaining natural teeth and/or the mucosa of the mouth. Consequently, there are some grave defects such as a feeling of physical disorder to the prosthesis used, degradation of the taste as a result of taste receptors scattered among the mucosal tissue of the mouth being covered with the denture, and absorption of the alveolar ridge during an extended use of the prosthesis.
To eliminate these problems, a dental implant procedure has been developed and put to practical use, according to which an implant fixture that functions as a combined retainer and stabilizer for prostheses is fitted and fixed in a cavity formed in the bone of toothless gum sites to serve as the roots of natural teeth, and is provided with a prosthesis retainer to which a prosthesis is fixedly attached.
This dental implant procedure has one advantage of eliminating a feeling of physical disorder to the prosthesis used or degradation of the taste; achieving a feeling of use similar to that of natural teeth, because the prosthesis can be fixed without covering the mucosa of the mouth. Another advantage is that it is possible to minimize deossification that might be induced with no implant fixture fitted, because a suitable occlusal force is imparted to the jawbone. For these reasons, the dental implant procedure has showed a rapid progress to such an extent that it is now applicable to gum sites with one tooth or two or more teeth extracted or otherwise lost, and anodontia.
In the dental implant procedure, however, there is need of a surgical operation in which the bone of the toothless gum site is provided with a cavity to receive the implant fixture, and the implant fixture is fitted in the cavity followed by suture of the surrounding gum of the cavity. Thus, the implant fixture must conform to aseptic and uncontaminative conditions, and has not only good bondability to the jawbone when fitted in the cavity but also good bio-affinity.
In most cases, the dental implant procedure is usually carried out by a dual-operation manner comprising a first operation for forming a cavity in the jawbone of a toothless gum site and fitting an implant fixture in the cavity to have a sufficient bond to the jawbone, and a second operation in which, after the recovery of the surgically operated site, the gum site on the intra-oral side of the cavity is again incised to fix on the intra-oral side of the cavity an abutment that provides a mount for a prosthesis retainer. At the first operation, a pre-operation is needed, in which a cover is attached to the implant fixture to close up a threaded hole for fixing the abutment on the intra-oral side of the implant fixture and so prevent the penetration of the bone. Thus, the cover is attached to the implant fixture by threaded engagement within the threaded hole formed in the intra-oral side of the implant fixture.
Care must be taken in fitting the implant fixture in the cavity. This is because when the implant fixture is fitted too deeply in the cavity, the jawbone grows to the intra-oral side of the cover; at the second operation it is required to incise not only the epithelial gum but the cured bone as well, and when the fitting depth of the implant fixture into the cavity is too shallow, the suture of the epithelial gum is difficult, since the cover is located too deeply in the intra-oral side. Especially when the portion of the implant fixture to be fitted in the bone is in a columnar form, the fitting of the implant fixture into cavity formed in the bone of a toothless gum site is usually carried by press fitting. However, the as-formed cavity is relatively labile, it is required that press fitting take place in an accurate direction at a reasonable pressure.
An object of the present invention is to provide an implant fixture that can be easily fitted in a cavity formed in the bone of a toothless gum site with no damage to the cavity, and an implant fixture forceps that enables the implant fixture to be easily fitted in a cavity formed in the bone in an aseptic, uncontaminative yet safe manner.